The present invention relates to hand held compasses and dip angle readers in general and, more particularly to a portable unit capable of measuring the azimuth of geological features where the local magnetic field is distorted.
Traditionally, common hand held compasses consist essentially of a circular body or case, a magnetized metallic pointer (needle) freely pivotally mounted with the body and a series of angular notations (degrees) circumscribing the pointer. The compass needle always aligns itself to the local expression of the earth""s magnetic field north-south axis. On some models, a bubble level indicates when the compass case is positioned parallel to the horizontal plane.
Examples of commercially available units are the Breithampt and Sohn stratum compass number 3019 xe2x80x9cGekom(trademark) (Kessel, Germany) and the Freiberger stratum compass xe2x80x9cF409xe2x80x9d(trademark) (ASC Scientific, Calsbad, Calif.).
U.S. Pat. No. 6,243,660 to Hsu et al., depicts a hand held multiple-use compass having digital sensors and a laser beam for sighting.
U.S. Pat. No. 5,531,031 to Green discloses an electronic inclinometer having a rotatable laser. The laser establishes a precision reference plane for measurement.
German patentschrift 30355 to Von Paschwitz apparently shows a late nineteenth century portable magnetic compass with its body protected by a flip cover.
Normally, to acquire structural data, geologists use magnetic compasses. However, when working in areas where the magnetic field is distorted; that is, near magnetic rocks, in underground excavations such as mines and tunnels, or in metallic structures, the accuracy and precision of these measurements is highly compromised. In such areas, the use of a magnetic compass is foreclosed.
However, the geologist may be required to measure structural features in such environments in order to characterize the behavior of the rock. In such circumstances, the geologist must rely on making a visual estimation of a structure""s azimuth. Alternatively, the geologist must use more time-consuming and expensive methods. Detailed structural work in underground environments has generally been avoided because of the lack of proper tools to accurately measure the orientation of lines and planes.
Accordingly, there is a need for a portable direction measuring apparatus that operates independently of the earth""s magnetic field.
There is provided a flexible modular compass that uses simple geometric rules to determine the true dip-direction (azimuth), and the dip-angle of planes and lines observed on rocks. The compass includes a laser pointer rotatably mounted in a hinged case. It is a modular design that allows easy convertible interchange between the laser pointer module and an alternate magnetic-needle module, as required. The laser module is ideal for magnetically compromised locations or in low-light environments.